This invention relates to a thread storage and supply device, preferably for textile machines, having a storage for positive thread supply preceded by a storage for intermittent thread supply.
Such an arrangement is selected to achieve especially low and regular output tension on the thread from the positive storage. It has hitherto been common in practice to let the known intermittent storage means operate together with a separate positive storage, e.g. a band storage. This solution is wasteful in terms of the space required.
The object of the invention is to provide a device of the type cited at the outset which is very simple and space-saving in construction.
This invention provides a thread storage and supply device in which a storage for intermittent thread supply and a storage for positive thread supply are combined. Both storages are known per se (East German patent specification No. 83 007 and German Auslegeschrift No. 2 160 161). In this invention, only a single shaft is required, and the space required is thus small. The path of the thread from the intermittently operating storage to the positive storage is very short and is accommodated in the hollow shaft in a space-saving and reliable manner. The device in accordance with the invention can, of course, be employed for purely intermittent thread supply if the thread is conducted from the hollow shaft directly to the processing station without having to pass through the positive storage. Likewise, the positive storage can be utilized alone if the thread is supplied directly to the hollow shaft from the storage bobbin without passing over the intermittent storage drum. It is possible to switch these three different modes of operation in a very simple and rapid manner. The present invention, however, is concerned only with the integrated device in its entirety and not with each individual storage respectively.
In a preferred embodiment, a common drive means is provided for the positive thread drum and for the winding element of the intermittent storage drum, said drive means being switchable in response to the stored amount of thread such that it drives only the positive thread drum when a predetermined maximum amount on the intermittent storage drum has been reached, whereas it also drives the winding element when the intermittent thread storage falls below a predetermined minimum amount. The result is a simple structure since, in addition to a single drive means, certain switching and control elements are required only once.
The external diameter of the intermittent storage drum, at least in the winding area, can advantageously be greater than that of the positive thread drum in the winding area. This makes it possible to drive the positive thread drum and the winding element of the intermittent storage drum at the same angular speed so that the forces which occur as well as the rotating elements cannot influence one another. Due to the synchronous operation of the positive thread drum and of the winding element, one respective winding is applied both to the positive thread drum as well as to the intermittent storage drum in the same period of time, in which time, however, less than one winding is removed from the intermittent storage drum due to the circumferential difference therebetween. Hence, the amount of the circumferential difference determines the rate at which a thread storage is formed or supplemented on the intermittent storage drum.
In a preferred embodiment, the opposed areas of the positive thread drum and the winding element are closely adjacent and have the same external diameter so as to share a common driving surface for a common driving element. The space required is especially small in this case. The construction costs are reduced still further, since the costs of auxiliary devices such as control elements and the like are lower for a single driving element.
In a preferred embodiment, the drive means includes an endless drive belt and the adjacent areas of the winding element and the positive thread drum have as the driving surface annular notches which supplement one another to form a groove corresponding to the belt cross section, and the positive thread drum has another annular groove corresponding to the belt cross section in axially spaced relation to the area adjacent said winding element. If the drive belt engages the groove common to the winding element and the thread drum, it drives both elements. If the drive belt is inserted into the groove belonging only to the positive thread drum, it acts as a drive means only for the thread drum and the winding element remains stationary. Hence, in order to switch over, it is not necessary to selectively drive two different drive elements, but rather a single adjustable driving element, which is driven continuously as long as thread is required, is sufficient for the double function.
The switch-over is possible in a simple manner in that the drive means is associated with at least one guide roller for the drive belt which is displaceably disposed at a distance corresponding to the spacing of the grooves, and that the drive means comprises an accumulator which engages in one direction as well as an electromagnet which upon excitation engages in the opposite direction and which can be energized and de-energized in response to the amount of thread on the intermittent storage drum. The height adjustment of the drive belt and thus the inclusion and exclusion of the intermittently operating yarn storage winding element thus necessitates only low construction costs and requires only elements which are simple in operation but nevertheless robust. The electromagnet can be switched reliably by a conventional monitor on the intermittent storage drum. The entire drive means can be arranged easily and in a space-saving manner in the area of the device.